Rotary piston engine with exhaust recirculating device

ABSTRACT

A rotary piston internal combustion engine provided with an exhaust recirculating device for effecting the reduction of both the nitrogen oxide content and the noxious unburned compounds present in the automobile exhaust gas and concurrently improving the engine power output with efficient fuel consumption by recirculating a portion of the exhaust gas from the engine working chamber under the power stroke to the engine working chamber under the compression stroke in response to the rotation of the power output shaft.

United States Patent 91 Shimizu Jan. 8, 1974 ROTARY PISTON ENGINE WITHEXHAUST RECIRCULATING DEVICE [7S] lnventor:

[73] Assignee: Toyo Kogyo Co., Ltd., Hiroshima-ken, Japan [22] Filed:Dec. 16, 1971 [21] App]. No.: 208,746

Hiroshi Shimizu, Hiroshima, Japan [30] Foreign Application Priority DataDec. 21, 1970 Japan 45/116179 [52] US. Cl 123/8.45, 60/278, 123/119 A[51] Int. Cl. F02b 53/06 [58] Field of Search l23/8.0l, 8.13, 8.45,

[56] References Cited UNITED STATES PATENTS 3,168,078 2/1965 Lamml23/8.l3

8/1972 Tatsutomi 123/119 A l/l972 Nakajima et a] 123/119 A PrimaryExaminer-Carlton R. Croyle Assistant Examiner-Michael Koczo, Jr.AttorneyCraig, Antonelli & Hill [57] ABSTRACT A rotary piston internalcombustion engine provided with an exhaust recirculating device foreffecting the reduction of both the nitrogen oxide content and thenoxious unburned compounds present in the automobile exhaust gas andconcurrently improving the engine power output with efficient fuelconsumption by recirculating a portion of the exhaust gas from theengine working chamber under the power stroke to the engine workingchamber under the compression stroke in response to the rotation of thepower output shaft.

23 Claims, 4 Drawing Figures PATENTEB JAN 81974 SHEET 2 [IF 3 5:29 t9 329.5 A|l 05 9 Qom 89 DE 25 3 w i u a i r: I I i ,K 31 {Ev I I l I P E-,%m [1w 2 E 3m M 3 2 05 Q3 8 .0? Q3 2 0% 9w ow 08 6% 0? 8m EMT T g om68; m o8 I I I I I I I Ill l l I n lflf f I ll -l 1" II II V I \I/ 3 \VAA b H AAA m A y A W H W W x 7 N w H z W V W m V W r\ w 9m PAIENTEBJAN8l974 3.783.839

saw 3 0r 3 ROTARY PISTON ENGINE WITH EXHAUST RECIRCULATING DEVICE Thepresent invention relates to an improvement in rotary piston internalcombustion engines and, more particularly, to an improved internalcombustion engine of this type wherein an exhaust recirculating deviceis disposed for recirculating a portion of the exhaust gas into thecompression chamber.

Current public attentions are centered on the air pollution problem andan exhaust gas emerging from an exhaust system of an automobile isconsidered one of the most significant sources of atmospheric pollutionin many cities of the world. Nevertheless, the automobile exhaust gas iscomposed of various kinds of chemical compounds and, of them, carbonmonoxide, hydrocarbon and nitrogen oxide are major constituents as havebeen largely admitted. I

It is generally well recognized that the amount of carbon monoxideand/or hydrocarbon present in the exhaust gas produced by the rotarypiston internal combustion engine is somewhat greater than orsubstantially equal to that produced by the reciprocating pistoninternal combustion engine, whereas the amount of nitrogen oxide presentin the exhaust gas produced by the rotary piston internal combustionengine is smaller than that produced by the reciprocating pistoninternal combustion engine. On the other hand, the current technologicallevel is such that elimination of reduction of the carbon monoxideand/or hydrocarbon contents can be easily achieved by the provision of acatalitic converter and/or thermal reactor (afterburner) for purifyingthe exhaust gas while that of the nitrogen oxide content is difficultand, if not difficult, limited.

As is well known to those skilled in the art, the typical model ofrotary piston engine in which the power output is produced by theplanetary motion of a rotary piston within a housing comprises a housingstructure having axially spaced end walls and a peripheral wallinterconnecting the end walls to form a cavity therebetween, and atriangular or other shaped multi-sided rotary piston rotatably mountedin said cavity and coaxially journalled with and on an eccentric portionof a shaft which extends axially through the center of the cavity andcoaxially journalled in the end walls of the housing to produceplanetary motion of the rotary piston during rotation of the shaft.Theperipheral wall has an epitrochoidal-shaped inner surface and has atleast two circumferentially spaced lobes. In this rotary piston engine,the four cycles of intake, compression, power and exhaust are carriedout simultaneously around the rotary piston when the engine is running.At this time, each of a plurality of working chambers respectivelydefined between arcuate flanks of the shaped rotary piston and theepitrochoidal-shaped inner surface of the peripheral wall within thecavity is successively conditioned in the intake, compression, power andexhaust strokes and varys in volume as the shaped rotary pistonundergoes the planetary motion.

In the conventional rotary piston engine of the above construction, theatomized fuel-air mixture that has been introduced into one of theworking chambers conditioned in the intake stroke has a tendency to be,because of the mass of fuel such as gasoline and the particular shape ofthe working chamber, separated into fuel and air at the rear or trailingzone of the working chamber at the time and after said working chamberhas become conditioned in the compression stroke, whereby the mixtureratio is differentiated between the trailing zone and the leading zonewithin the working chamber in such a way that said ratio at the trailingzone is relatively greater than that at the leading zone. This hampersinstantaneous perfect combustion of the mixture during the nextsucceeding power or combustion stroke in view of the fact that adevelopment of combustion during the ignition is retarded at thetrailing zone in which the richer mixture is accumulated. Accordingly,not only the power output of the engine is reduced, but also a somewhatgreater amount of fuel is wasted, as compared with those afforded by thereciprocating piston engine.

To eliminate the nitrogen oxide content in the exhaust gas, it has beenrecently proposed to provide the automobile exhaust recirculating devicein the rotary piston engine, by which a portion of the exhaust gas isrecirculated into the intake manifold or the intake port of the engine.In this case, there can be found a disadvantage in that, as that portionof the exhaust gas is supplied to the intake manifold or the intake portof the engine, the flow of the effective mixture from a source of themixture to the combustion chamber has a tendency to be hampered in sucha way that a portion of the effective mixture which corresponds to theamount of the exhaust gas thus recirculated is sacrificed, i.e., can notbe supplied. This badly affects the volumetric efficiency.

Accordingly, one essential object of the present in- I vention is toprovide an improved rotary piston internal combustion engine having anexhaust recirculating device by which the fuel-air mixture that has beensupplied to the working chamber in the compression stroke can beuniformly distributed so that the combustion efficiency and, therefore,the power output of the engine can be substantially improved without themixture consumed so much as has been heretofore required.

Another object of the present invention is to provide an internalcombustion engine of the above type having an exhaust recirculatingdevice by which the amounts of the nitrogen oxide content generallypresent in the exhaust gas can be reduced to an appreciable valuesmaller than that emitted from the conventional rotary piston internalcombustion engine.

A further object of the present invention is to provide an internalcombustion engine of the above type having an exhaust recirculatingdevice by which a reduction of the volumetric efficiency can beeliminated to improve the power output of the engine.

A still further object of the present invention is to provide aninternal combustion engine of the above type having an exhaustrecirculating device which can be manufactured at low cost withsimplified structure and which can be installed in the conventionalengine of this kind. I

7 According to the present invention, a portion of the exhaust gas ofthe rotary piston internal combustion engine is circulated from one ofthe working chambers, which is conditioned in the power stroke intoanother one of the working chambers which is conditioned in thecompression stroke, by the effect of the pressure differential betweensaid two working chambers. To determine the timing of supply and theamount of that portion of the exhaust gas to be circulated into theworking chamber conditioned in the compression stroke, means is alsoprovided for valving the connection between said working chamber underthe power stroke and the working chamber under the compression stroke.In the preferred embodiment of the present invention, this valving meansis adapted to operate in response to the rotation of the output shaft ofthe engine.

These and other objects and features of the present invention willbecome apparent from the following description thereof made inconjunction with preferred embodiments thereof shown in the accompanyingdrawings, in which;

FIG. 1 is a side elevation of the mechanism in one embodiment of thepresent invention with one end wall of the engine housing being removedto show the rotary piston position therein,

FIG. 1A is an enlarged fragmentary view of FIG. 1,

FIG. 2 is a performance curve showing variations in pressure in theworking chambers of the rotary piston internal combustion engine, whichis used to illustrate the operation of the present invention, and

FIG. 3 is a similar view to FIG. 1, showing another combustion engine asshown includes a peripheral housing 1 having an epitrochoidal innersurface. A pair of side walls is disposed on the both sides of theperipheral housing 1, only one of which is shown and indicated by 2. Arotary piston 3 formed with three arcuate flanks and forming a trianglein cross-section is rotatably supported by an eccentric portion 4a of apower output shaft 4 and rotates under planetary motion within thecavity defined by the peripheral housing 1 and the side walls. Apexseals 5, and side seals 6 and 7 maintain a plurality of working chambersin the airtight condition, said working chambers being defined betweenthe inner surface of the peripheral housing 1 and the arcuate flanks ofthe rotary piston 3 as the latter undergoes the planetary motion. An oilseal 8 is fixed to the rotary piston 3 in such a manner as to surround acentral opening 9, of the diameter substantially equal to that of theeccentric portion 4a, so that oil can be prevented from leaking radiallyoutwardly through the space between the side walls 2 and the rotarypiston 3. The peripheral housing 1 is also formed with a small openingfor accommodating therein an ignition plug 10. An exhaust port 11 forexhausting an exhaust gas therethrough to the outside of the housing 1and an intake port 12 through which a fresh fuel-air mixture is suppliedare, in the instance as shown, formed in the housing 1 and one of theside walls 2 in a suitably spaced relation with respect to each other,respectively.

The structural features of the rotary piston internal combustion engineso far described is well known to those skilled in the art and,therefore, the details are herein omitted. However, it is to be notedthat the working chambers cyclically vary in volume during the planetarymotion of the rotary piston 3 for the performance of a series of intake,compression, power or combustion and exhaust stroke as is also known tothose skilled in the art.

The present invention is directed to the connection between one of theworking chambers, which is conditioned in the power stroke, to anotherone of the working chambers which is conditioned in the compressionstroke, namely, between the chamber A to the chamber B in the instanceas shown. This connection includes a first passage 13 having one endconnected with an exhaust gas inlet port 14 formed, for example, in theside wall 2 at a position corresponding to the trailing zone of theworking chamber under the compression stroke, and a second passage 15having one end connected with an exhaust gas outlet port 16 formed, forexample, in the side wall 2 at a position corresponding to the leadingzone of the working chamber under the power stroke and the other endconnected with the other end of the first passage 13 through means forvalving the connection between said first and second passages 13 and 15in response to the rotation of the power output shaft 4. Disposed on thesecond passage 15 between said exhaust gas outlet port 16 and thevalving means, generally indicated by 17, is a pressure control valve ofsuitable construction, the function of which will be mentioned later.

The valving means 17 is in the instance as shown composed of a passage18 formed in a free end of the output shaft 4 which is remote from theother'end thereof connected in an operative manner with a wheel drivingshaft (not shown) through a suitable transmission (also not shown), anda cap-like bearing 19 having a peripheral wall of the inner diametersubstantially equal to the diameter of the free end of the power outputshaft 4 and a bottom portion rigidly connected with one end of theperipheral wall as shown.

The passage 18 formed in the free end of the power output shaft 4includes a portion 18a axially extending through the center of said freeend of said shaft 4 and another portion 18b extending at right angles tosaid first mentioned portion 18a. This passage 18 has one end connectedwith the adjacent end of the first passage 13 through a hole 17a formedin the peripheral wall of the cap-like bearing 19 in register therewithand the other end connected with the adjacent end of the second passage15 through a hole 17b formed in the bottom portion of said bearing 19 inregister therewith. The bearing 19 is fixed to a suitable rigid portionof the engine body or a suitable portion of a vehicle structure in anyknown manner while rotatably accommodating therein the free end of thepower output shaft 4. It is to be noted that the second passage 15 ispermanently connected with the passage 18, formed in the free end of theshaft 4, through the hole 17b formed in the bottom portion of thebearing 19.

This valving means 17 of the above construction is operable in responseto the rotation of the power output shaft 4 in such a way that theconnection between the first and second passages 13 and 15 can beestablished through the passage 18 each time the shaft 4 is rotatedthrough a certain angle, the value of said angle being such that, eachtime the opening 16 that has been closed by the rotary piston 3 isopened, the flow of a portion of the exhaust gas from the workingchamber under the power stroke to the working chamber under thecompression stroke is permitted through said valving means.

The pressure control valve 20 disposed on the second passage is of thetype designed such as to regulate the pressure of the exhaust gassupplied thereto to a value slightly higher than the value of pressureexerted by the compression of the fuel-air mixture in the workingchamber under the compression stroke, whereby not only the backflow ofthe mixture from the chamber under the compression stroke to the chamberunder the power stroke can be prevented, but also a possible occurrenceof considerable turbulence and vortex flow of the mixture in the chamberunder the compression stroke which is attributable to the excessivelyhigh gas pressure can be prevented.

In constructing the device according to the present invention, care mustbe taken in the design of the exhaust gas inlet port 14 which is shownas formed in the end wall 2, but may be formed in the peripheral housing1 at the corresponding position. In view of the fact that one of theessential features of the present invention resides in the adjustment ofthe enriched mixture at the trailing zone of the chamber under thecompression stroke to a substantially proper ratio of fuel to airthereby to eliminate the unevenness of the mixture ratio within saidworking chamber, the port 14 is preferably oriented such that a portionof the exhaust gas supplied from the working chamber under the powerstroke and emerging from said port 14 flows in the opposite directionsat right. angles relative to the axis of the power output shaft 4 andrearwardly with respect to the trailing zone of the working chamberunder the compression stroke, substantially indicated by the arrows inan enlarged fragmentary view of FIG. 1. With this design, the mixturepresent at the leading zone of the chamber under the compression strokecan be advantageously prevented from leaning which may results from thesupply of the exhaust gas into the chamber under the compression stroke.

The operation of the device according to the present invention will behereinafter described with reference to FIG. 2 in combination with FIG.1 and, in the course thereof, an attempt is made to clarify theoperation of the valving means 17. As is well known to those skilled inthe art, when the rotary piston internal combustion engine is running,the four cycles of a series of intake, compression, power and exhaustcan be repeated a number of times during one planetary motion of therotary piston. However, so far as a single working chamber definedwithin the housing cavity between each arcuate flank of the rotarypiston and the inner surface of the peripheral housing is involved, thecompletion of the four cycles or one planetary motion results inrotation of the power output shaft through 1,080. During the four cyclesof the working chamber, the value of pressure present within saidchamber varys such as shown in FIG. 2 wherein the axis of ordinaterepresents the pressure in the working chamber while the axis ofabscissa represents the angle of rotation of the power output shaft 4together with the timing of operation of various components of therotary piston engine as defined below;

TDC: Piston 3 is in the Top Dead Center position.

E0: Exhaust port 11 is Opened.

. 'BDC: Piston 3 is in the Bottom Dead Center position.

[0: Intake port 12 is Opened. EC: Exhaust port 11 is Closed.

IC: Intake port 12 is Closed. and reference characters X, Y and Z givento the curves are assumed to represent respectively as follows;

X: Pressure variation within the working chamber defined between theflank 3a of the piston 3 andthe inner surface 1a of the peripheralhousing 1,

Y: Pressure variation within the working chamber defined between thepiston flank 3b and the housing inner surface 1a, and

Z: Pressure variation within the working chamber defined between thepiston flank 3c and the housing inner surface 1a.

With the above in mind, attention is first called to the pressurevariation within the working chamber defined between the flank 3a of thepiston 3 and the inner surface 1a of the peripheral housing 1.

As represented by the curve X, the pressure commences to increase fromthe minimum value upon closure of the intake port 12 at IC andthereafter increases. At TDC, the ignition plug 10 is operated to effecta combustion of the mixture contained in said chamber whereby thepressure can be rapidly increased to the maximum value and said workingchamber has been brought into the power stroke. This power strokecontinues until the exhaust port 11 is opened-at EO at which time thechamber is brought into the exhaust stroke. However, it is to be notedthat, in view of the fact that the exhaust port 11 is graduallyopened'to its full open position as is well known to those skilled inthe art, the pressure at the time of opening of the port 1 1 remains atthe value P which is still higher than the minimum value. Then, theintake port 12'opens at IO to enter the working chamber, that has beenconditioned in the exhaust stroke, into the intake stroke and theexhaust port 11 closes at EC to complete the exhaust stroke. Thus, it isclear that, during a series of intake, compression, power and exhauststrokes, the output shaft 4 can be rotated through 1,080 as hereinbeforedescribed.

The pressure variations within the other working chambers definedbetween the piston flank 3b and the housing inner surface 1a and thepiston flank 3c and the housing inner surface 1a, respectively, asrepresented by the curves Y and Z, are displaced in phase 360 and 720respectively with respect to the pressure variations within the workingchamber defined between the piston flank 3a and the housing innersurface In.

In practice, the chamber defined by the flank 3b is,

so far as it is related with respect to the leading chamber defined bythe flank 3a, in the intake stroke at the time when the chamber definedby the flank 3a is to be brought into the power stroke past TDC. Thechamber defined by the flank 3b can be completely brought into thecompression stroke upon closure of the intake port 12 at IC, duringwhich the chamber defined by the flank 3a is still in the power strokewhich will complete upon opening of the exhaust port 11. In thisinstance, the pressure within the chamber defined by the flank 3a ishigher than that within the chamber defined by the flank 3b. In otherwords, the pressure within the chamber under compression stroke is lowerthan that within the chamber under power stroke. Accordingly, duringthis period, by the effect of pressure differential between thesechambers respectively under the power and compression strokes, a portionof the exhaustgas can be supplied to the chamber under the compressionstroke by means of the passage 15 and then the passage 13 through thevalving means 17, the supply of that portion of the exhaust gas from thechamber under the power stroke to the chamber under the compressionstroke being continued until the chamber under the power stroke isbrought into the exhaust stroke, namely, until the time when the exhaustport 11 is opened, substantially as indicated by the hatching in FIG. 2.

At this time, since the temperature of the exhaust gas thus supplied isof a relatively higher value, the deposit of fuel wetted on the flank ofthe piston 3 and the inner surface 1a of the housing 1 which define thechamber under the compression stroke can be advantageously vaporized bythe effect of said temperature. In addition, since the inlet port 14 is,of course, oriented such as hereinbefore described, the leaning of themixture within the leading zone of the chamber under the compressionstroke can also be advantageously eliminated.

In view of the foregoing, reduction of the engine power output can beprevented and, concurrently,.

emission of a considerable amount of noxious un burned compounds, aswell as nitrogen oxide, present in the exhaust gas to the atmosphere canbe prevented, even though a portion of the exhaust gas has been suppliedin the manner as hereinbefore fully disclosed. Especially, the noxiousunburned compounds can be more reduced if the thermal reactor orafterburner is operatively provided with the engine of the presentinvention.

In FIG. 3, another preferred embodiment of the pres ent invention isshown. The structure of the engine shown in FIG. 3 is substantially thesame as shown in HO. 1 except for the provision of an electricallyoperated solenoid valve 30 of any suitable construction.

The solenoid valve 30 is operatively disposed on the second passage 15at a position between the valving means 17 and the pressure controlvalve 20 for the purpose of preventing the mixture in the chamber underthe compression stroke from being diluted during the engine warm-uporidling. This is because, during such period, the somewhat enrichedmixture is recommended in the working chamber under the compressionstroke to facilitate the start of the engine or stabilize the idling.Accordingly, this solenoid valve'30 is operable in such a manner that,only during this period, the passage 15 is cut off thereby.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof, various changes andmodifications are apparent to those skilled in the art. For example, thevalving means 17 shown as formed in'the free end of the power outputshaft 4 in the foregoing embodiments may be replaced with anotherelectrically operated solenoid valve capable of performing the samefunction as performed by said valving means. In this case, theelectrically operated solenoid valve is preferably operated in responseto the rotation of the shaft 4 as well. In addition, in view of the factthat the temperature of the exhaust gas is relatively higher, a coolingdevice may be disposed on the connection between the chambersrespectively under the compression and power strokes thereby to reducethe temperature to a value proper to the chamber under the compressionstroke.

What is claimed is:

l. A rotary piston internal combustion engine comprising a housinghaving spaced end walls and a peripheral wall between said end walls andhaving an epitrochoidal inner surface forming a cavity, said housingbeing formed with spaced intake and exhaust ports and an ignition plugextending through said housing at a point spaced there-around from saidports; a rotary piston having at least three side flanks andeccentrically rotatably mounted on a power output shaft within saidcavity, said rotary piston having circumferentially spaced apexes andsubstantially flat end faces at opposite ends thereof, each of saidapexes and flat end faces having sealing members slidably engaged withthe inner surface of said housing to form between the rotary piston andthe housing a plurality of working chambers, each of said workingchambers being capable of varying in volume during the planetary motionof said rotary piston performing each four strokes of intake,compression, power and exhaust; connecting means connecting one of saidworking chambers, which is conditioned in the power stroke, to thetrailing zone of another one of said working chambers, which isconditioned in the compression stroke; and a valving device disposed insaid connecting means and operable in response to rotation of the poweroutput shaft to supply a portion of exhaust gas present in said workingchamber under the power stroke to said working chamber under thecompression stroke in a predetermined timing by the effect of pressuredifferential between said two working chambers respectively under thepower and compression strokes, thereby permitting re-mixing of thefuel-air mixture, that has been supplied tosaid working chamber underthe compression stroke, with that portion of said exhaust gas forreducing the nitrogen oxide content present in the exhaust gas andimproving an efficient fuel consumption with substantial increase of theengine power output.

2. A rotary piston internal combustion engine as claimed in claim 1,wherein said connecting means includes a first passage having one endopen to the working chamber under the compression stroke, a secondpassage having one end connected with the other end of said firstpassage through said valving device and the other end open to theworking chamber under the power stroke, and a pressure control valvedisposed in one of said first and second passages for regulating thepressure of that portion of the exhaust gas permitted to flow throughsaid passages.

3. A rotary piston internal combustion engine as claimed in claim 2,wherein said valving deviceis formed in a free end of the power outputshaft.

4. A rotary piston internal combustion engine as claimed in claim 2,wherein one of said first and second passages includes another valvingdevice operatively disposed thereon for preventing the supply of thatportion of the exhaust gas during at least the engine warmup period andthe idling period even though said valving device designed to determinethe amount of and the timing of the supply of that portion of theexhaust gas in response to the rotation of the power output shaft hasbeen brought in the position to permit the flow of that portion of theexhaust gas therethrough.

5. A rotary piston internal combustion engine as claimed in claim 2,wherein said end of said first passage which is opened to the workingchamber under the compression stroke is oriented such that the portionof the exhaust gas supplied thereto flows into the working chamber underthe compression stroke in the opposite directions at right anglesrelative to the axis of the power output shaft and rearwardly withrespect to a trailing zone of the working chamber under the compressionstroke.

6. A rotary piston internal combustion engine comprising a housinghaving spaced end walls and a peripheral wall between said end walls andhaving an epitrochoidal inner surface forming a cavity, said housingbeing formed with spaced intake and exhaust ports and an ignition plugextending through said housing at a point spaced therearound from saidports; a rotary piston having at least three side flanks andeccentrically rotatably mounted on a power output shaft within saidcavity, said rotary piston having circumferentially spaced apexes andsubstantially flat end faces at opposite ends thereof, each of saidapexes and flat end faces having sealing members slidably engaged withthe inner surface of said housing to form between the rotary piston andthe housing a plurality of working chambers, each of said workingchambers being capable of varying in volume during the planetary motionof said rotary piston performing each four strokes of intake,compression, power and exhaust; a first passage having one end open toone of said working chambers which is conditioned in the compressionstroke; a second passage having one end open to another one of theworking chambers which is conditioned in the power stroke; a pressurecontrol valve disposed on said second passage for regulating thepressure of a portion of exhaust gas to be supplied from said workingchamber under the power stroke to said working chamber under thecompression stroke and a valving device for connecting said first andsecond passage and operable to permit the flow of said portion of saidexhaust gas in a proper timing and in a suitable amount by the, effectof pressure differential between said two working chambers under thepower and compression stroke, whereby remixing of the fuel-air mixturethat has been supplied to said working chamber under the compressionstroke can be performed for reducing the nitrogen oxide content presentin the exhaust gas and improving an efficient fuel consumption withsubstantial increase of the engine power output.

7. Exhaust gas recirculating apparatus for an internal combustion engineof the type having a rotary piston drivingly connected to an engineoutput shaft and rotatable within an engine housing in such a mannerthat a plurality of variable volume working chambers are formed betweencirc umferentially spaced apices of said piston and inner surfaces ofsaid engine housing, each of said working chambers being variable involume during rotation of said piston to sequentially experience intake,compression, power and exhaust stroke conditions, each of said workingchambers exhibiting a leading zone and a trailing zone delimited byrespective ad jacent apices of the piston in the direction of travel ofthe piston; said apparatus comprising connecting means for conducting aportion of the exhaust gases from a first of said working chambers whichis experiencing a power stroke condition to a second of said workingchambers which is experiencing a compression stroke condition, whereinsaid connecting means communicates with said second working chamber onlyby way of inlet means at a position corresponding to the trailing zoneof said second chamber, whereby the inherently richer fuel to airmixture occurring in said trailing zone of said second chamber isdiluted by the exhaust conducted from said first chamber to moreuniformly distribute the fuel to air mixture in said second chamber witha consequent increase in efficiency of fuel consumption and engine poweroutput while reducing the nitrogen oxide content present in the engineexhaust gases.

8. Apparatus according to claim 7, wherein said connecting meanscommunicates with said first chamber at a position corresponding to theleading zone of said first chamber.

9. Apparatus according to claim 7, wherein said connecting meansincludes conduit means extending between said first and second chambersand a valving device for selectively opening and closing said conduitmeans, said valving device including means responsive to the rotationalposition of said engine output shaft and separate from any openings tosaid engine housing controlled directly by said piston for controllingthe amount of and timing of the opening of said conduit means.

10. Apparatus according to claim 9, wherein said' valving deviceincludes passage means extending through a portion of said engine outputshaft, one end of said passage means continuously communicating with afirst part'of said conduit means which is open to one of said first andsecond working chambers and the other end of said passage meansselectively communicating with a second part of said conduit means whichis open to the other of said first and second chambers in dependence onthe rotational position of said engine output shaft.

11. Apparatus according to claim 10, wherein said first part of saidconduit means is open to said second working chamber. I

12. Apparatus according to claim 9, further comprising a pressurecontrol valve disposed in said connecting means for regulating thepressure of the exhaust gases conducted between said first and secondworking chambers.

13. Apparatus according to claim 12, wherein said pressure controlvalve. includes means for preventing backflow of gases through saidconnecting means from said second working chamber to said first workingchamber. 4

14. Apparatus according to claim 10, further comprising a pressurecontrol valve disposed in said connecting means for regulating thepressure of the exhaust gases conducted between said first and secondworking chambers.

15. Apparatus according to claim 9, further comprising a second valvingdevice for closing said connecting ing conditions.

18. Apparatus according to claim 17, wherein said second valving deviceincludes means for closing said connecting means during engine idlingand warm-up conditions.

19. Exhaust gas recirculating apparatus for an internal combustionengine of the type having a rotary piston drivingly connected to anengine output shaft and rotatalable within an engine housing in such amanner that a plurality of variable volume working chambers are formedbetween circumferentially spaced apices of said piston and innersurfaces of said engine housing, each of said working chambers beingvariable in volume during rotation of said piston to sequentiallyexperience intake, compression, power and exhaust stroke conditions,each of said working chambers exhibitng a leading zone and a trailingzone delimited by respective adjacent apices of the piston in thedirection of travel of the piston, said apparatus comprising connectingmeans for conducting a portion of the exhaust gases from a first of saidworking chambers which is experiencing a power stroke condition to asecond of said working chambers which is experiencing a compressionstroke condition, wherein said connecting means includes conduit meansextending between said first and second chambers and a valving devicefor selectively opening and closing said conduit means, said valvingdevice including means responsive to the rotational position of saidengine output shaft and separate from any openings to said enginehousing controlled directly by said piston for controlling the amount ofand timing of the opening of said conduit means.

20. Apparatus according to claim 19, wherein said valving deviceincludes passage means extending through a portion of said engine outputshaft, one end of said passage means continuously communicating with afirst part of said conduit means which is open to one of said first andsecond working chambers and the other end of said passage meansselectively communicating with a second part of said conduit means whichis open to the other of said first and second chambers in dependence onthe rotational position of said engine output shaft.

21. Apparatus according to claim 20, further comprising a pressurecontrol valve disposed in said connecting means for regulating thepressure of the exhaust gases conducted between said first and secondworking chambers.

22. Apparatus according to claim 19, further comprising a second valvingdevice for closing said connecting means irrespective of the position ofsaid firstmentioned valving device during certain engine operatingconditions.

23. Apparatus accordingto claim 22, wherein said second valving deviceincludes means for closing said connecting means during engine idlingand warm-up conditions.

1. A rotary piston internal combustion engine comprising a housinghaving spaced end walls and a peripheral wall between said end walls andhaving an epitrochoidal inner surface forming a cavity, said housingbeing formed with spaced intake and exhaust ports and an ignition plugextending through said housing at a point spaced there-around from saidports; a rotary piston having at least three side flanks andeccentrically rotatably mounted on a power output shaft within saidcavity, said rotary piston having circumferentially spaced apexes andsubstantially flat end faces at opposite ends thereof, each of saidapexes and flat end faces having sealing members slidably engaged withthe inner surface of said housing to form between the rotary piston andthe housing a plurality of working chambers, each of said workingchambers being capable of varying in volume during the planetary motionof said rotary piston performing each four strokes of intake,compression, power and exhaust; connecting means connecting one of saidworking chambers, which is conditioned in the power stroke, to thetrailing zone of another one of said working chambers, which isconditioned in the compression stroke; and a valving device disposed insaid connecting means and operable in response to rotation of the poweroutput shaft to supply a portion of exhaust gas present in said workingchamber under the power stroke to said working chamber under thecompression stroke in a predetermined timing by the effect of pressuredifferential between said two working chambers respectively under thepower and compression strokes, thereby permitting re-mixing of thefuel-air mixture, that has been supplied to said working chamber underthe compression stroke, with that portion of said exhaust gas forreducing the nitrogen oxide content present in the exhaust gas andimproving an efficient fuel consumption with substantial increase of theengine power output.
 2. A rotary piston internal combustion engine asclaimed in claim 1, wherein said connecting means includes a firstpassage having one end open to the working chamber under the compressionstroke, a second passage having one end connected with the other end ofsaid first passage through said valving device and the other end open tothe working chamber under the power stroke, and a pressure control valvedisposed in one of said first and second passages for regulating thepressure of that portion of the exhaust gas permitted to flow throughsaid passages.
 3. A rotary piston internal combustion engine as claimedin claim 2, wherein said valving device is formed in a free end of thepower output shaft.
 4. A rotary piston internal combustion engine asclaimed in claim 2, wherein one of said first and second passagesincludes another valving device operatively disposed thereon forpreventing the supply of that portion of the exhausT gas during at leastthe engine warm-up period and the idling period even though said valvingdevice designed to determine the amount of and the timing of the supplyof that portion of the exhaust gas in response to the rotation of thepower output shaft has been brought in the position to permit the flowof that portion of the exhaust gas therethrough.
 5. A rotary pistoninternal combustion engine as claimed in claim 2, wherein said end ofsaid first passage which is opened to the working chamber under thecompression stroke is oriented such that the portion of the exhaust gassupplied thereto flows into the working chamber under the compressionstroke in the opposite directions at right angles relative to the axisof the power output shaft and rearwardly with respect to a trailing zoneof the working chamber under the compression stroke.
 6. A rotary pistoninternal combustion engine comprising a housing having spaced end wallsand a peripheral wall between said end walls and having an epitrochoidalinner surface forming a cavity, said housing being formed with spacedintake and exhaust ports and an ignition plug extending through saidhousing at a point spaced therearound from said ports; a rotary pistonhaving at least three side flanks and eccentrically rotatably mounted ona power output shaft within said cavity, said rotary piston havingcircumferentially spaced apexes and substantially flat end faces atopposite ends thereof, each of said apexes and flat end faces havingsealing members slidably engaged with the inner surface of said housingto form between the rotary piston and the housing a plurality of workingchambers, each of said working chambers being capable of varying involume during the planetary motion of said rotary piston performing eachfour strokes of intake, compression, power and exhaust; a first passagehaving one end open to one of said working chambers which is conditionedin the compression stroke; a second passage having one end open toanother one of the working chambers which is conditioned in the powerstroke; a pressure control valve disposed on said second passage forregulating the pressure of a portion of exhaust gas to be supplied fromsaid working chamber under the power stroke to said working chamberunder the compression stroke and a valving device for connecting saidfirst and second passage and operable to permit the flow of said portionof said exhaust gas in a proper timing and in a suitable amount by theeffect of pressure differential between said two working chambers underthe power and compression stroke, whereby re-mixing of the fuel-airmixture that has been supplied to said working chamber under thecompression stroke can be performed for reducing the nitrogen oxidecontent present in the exhaust gas and improving an efficient fuelconsumption with substantial increase of the engine power output. 7.Exhaust gas recirculating apparatus for an internal combustion engine ofthe type having a rotary piston drivingly connected to an engine outputshaft and rotatable within an engine housing in such a manner that aplurality of variable volume working chambers are formed betweencircumferentially spaced apices of said piston and inner surfaces ofsaid engine housing, each of said working chambers being variable involume during rotation of said piston to sequentially experience intake,compression, power and exhaust stroke conditions, each of said workingchambers exhibiting a leading zone and a trailing zone delimited byrespective adjacent apices of the piston in the direction of travel ofthe piston; said apparatus comprising connecting means for conducting aportion of the exhaust gases from a first of said working chambers whichis experiencing a power stroke condition to a second of said workingchambers which is experiencing a compression stroke condition, whereinsaid connecting means communicates with said second working chamber onlyby way of inlet means at a position corresponding to the trailing zoneof said second chamber, whereby the inherently richer fuel to airmixture occurring in said trailing zone of said second chamber isdiluted by the exhaust conducted from said first chamber to moreuniformly distribute the fuel to air mixture in said second chamber witha consequent increase in efficiency of fuel consumption and engine poweroutput while reducing the nitrogen oxide content present in the engineexhaust gases.
 8. Apparatus according to claim 7, wherein saidconnecting means communicates with said first chamber at a positioncorresponding to the leading zone of said first chamber.
 9. Apparatusaccording to claim 7, wherein said connecting means includes conduitmeans extending between said first and second chambers and a valvingdevice for selectively opening and closing said conduit means, saidvalving device including means responsive to the rotational position ofsaid engine output shaft and separate from any openings to said enginehousing controlled directly by said piston for controlling the amount ofand timing of the opening of said conduit means.
 10. Apparatus accordingto claim 9, wherein said valving device includes passage means extendingthrough a portion of said engine output shaft, one end of said passagemeans continuously communicating with a first part of said conduit meanswhich is open to one of said first and second working chambers and theother end of said passage means selectively communicating with a secondpart of said conduit means which is open to the other of said first andsecond chambers in dependence on the rotational position of said engineoutput shaft.
 11. Apparatus according to claim 10, wherein said firstpart of said conduit means is open to said second working chamber. 12.Apparatus according to claim 9, further comprising a pressure controlvalve disposed in said connecting means for regulating the pressure ofthe exhaust gases conducted between said first and second workingchambers.
 13. Apparatus according to claim 12, wherein said pressurecontrol valve includes means for preventing backflow of gases throughsaid connecting means from said second working chamber to said firstworking chamber.
 14. Apparatus according to claim 10, further comprisinga pressure control valve disposed in said connecting means forregulating the pressure of the exhaust gases conducted between saidfirst and second working chambers.
 15. Apparatus according to claim 9,further comprising a second valving device for closing said connectingmeans irrespective of the position of said first-mentioned valvingdevice during certain engine operating conditions.
 16. Apparatusaccording to claim 15, wherein said second valving device includes meansfor closing said connecting means during engine idling and warm-upconditions.
 17. Apparatus according to claim 12, further comprising asecond valving device for closing said connecting means irrespective ofthe position of said first-mentioned valving device during certainengine operating conditions.
 18. Apparatus according to claim 17,wherein said second valving device includes means for closing saidconnecting means during engine idling and warm-up conditions. 19.Exhaust gas recirculating apparatus for an internal combustion engine ofthe type having a rotary piston drivingly connected to an engine outputshaft and rotatalable within an engine housing in such a manner that aplurality of variable volume working chambers are formed betweencircumferentially spaced apices of said piston and inner surfaces ofsaid engine housing, each of said working chambers being variable involume during rotation of said piston to sequentially experience intake,compression, power and exhaust stroke conditions, each of said workingchambers exhibitng a leading zone and a trailing zone delimited byrespective adjacent apices of the piston in the direction of travel ofthe piston, said apparatus comprising connecting means for conducting aportion of the exhaust gases from a first of said wOrking chambers whichis experiencing a power stroke condition to a second of said workingchambers which is experiencing a compression stroke condition, whereinsaid connecting means includes conduit means extending between saidfirst and second chambers and a valving device for selectively openingand closing said conduit means, said valving device including meansresponsive to the rotational position of said engine output shaft andseparate from any openings to said engine housing controlled directly bysaid piston for controlling the amount of and timing of the opening ofsaid conduit means.
 20. Apparatus according to claim 19, wherein saidvalving device includes passage means extending through a portion ofsaid engine output shaft, one end of said passage means continuouslycommunicating with a first part of said conduit means which is open toone of said first and second working chambers and the other end of saidpassage means selectively communicating with a second part of saidconduit means which is open to the other of said first and secondchambers in dependence on the rotational position of said engine outputshaft.
 21. Apparatus according to claim 20, further comprising apressure control valve disposed in said connecting means for regulatingthe pressure of the exhaust gases conducted between said first andsecond working chambers.
 22. Apparatus according to claim 19, furthercomprising a second valving device for closing said connecting meansirrespective of the position of said first-mentioned valving deviceduring certain engine operating conditions.
 23. Apparatus according toclaim 22, wherein said second valving device includes means for closingsaid connecting means during engine idling and warm-up conditions.